A known undercarriage rocker arm that is shown schematically in FIG. 1 indicated by reference numeral 1 takes the form of a tubular part or an arm extending in a main direction indicated by AP.
This arm comprises a main portion 2 extending between two ends 3 and 4 and having a circular section that is approximately constant in its central region.
As can be seen in FIG. 1, the front end 3 of this arm is designed to receive a shaft oriented transversely in the direction AT that is in this instance perpendicular to the direction AP. This end therefore forms a portion forming an interface or bearing formed in two bosses protruding transversely from the outer face of the main body 2.
Each boss is pierced and bored in the direction AT, so as to form the two bearing surfaces of the bearing in order to engage a mechanical shaft passing transversely through the main body of the arm.
Similarly, the rear end also comprises an interface forming a generally similar bearing which is designed to receive another transverse shaft not shown. In addition, this rocker arm also comprises an intermediate crevice 8 situated between its two ends and protruding radially from the outer face of the main body.
Because of the complex shape of the bearings of such a rocker arm that can be seen in FIG. 1 and because of the considerable mechanical strength that is expected of it, the whole rocker arm is usually manufactured of high strength steel by machining.
The bosses 6 and 7 in which the bearings are made are determinant in that they constitute local extra thicknesses of material, which is indispensible for ensuring that the forces applied by the mechanical shaft on the rocker arm body do not give rise to concentrations of stresses that are too great in the rocker arm.
Therefore, in general, the structural elements of the rocker arm or a similar type require the production of extra thicknesses of material at their interfaces with other parts in order to limit the phenomenon of stress concentration that is likely to cause incipient cracks.
In the case of an undercarriage rocker arm like that of FIG. 1, each bearing receives a shaft that is in fact attached relative to the rocker arm and that forms an axle carrying for example two wheels situated on either side of this rocker arm.
The problem that arises is similar in the case of an arm comprising a bearing receiving a rotary shaft, because the question of concentration of stresses at the bearing remains determinant with respect to the dimensioning of such an arm.